Gaseous cold cathode indicator tube having a segmented electrode and an insulating shield plate



1966 T. c. MALONEY ETAL 3,280,359

GASEOUS COLD CATHODE INDICATOR TUBE HAVING A SEGMENTED ELECTRODE AND ANINSULATING SHIELD PLATE Filed May 20, 1965 2 Sheets-Sheet 1 4 INVENTORSTHOMAS C. MALONEY JAMES T. BUYER M6. M 2 M ATTORNEY Oct. 18, 19663,280,359 MENTED T. C. MALONEY ETAL GASEOUS COLD CATHODE INDICATOR TUBEHAVING A SEG ELECTRODE AND AN INSULATING SHIELD PLATE 2 Sheets-Sheet 2Filed May 20, 1963 INVENTORS THOMAS C. MALONEY JAMES T. BOYER ATTORNEYUnited States Patent 3,280,359 GASEOUS COLD CATHODE INDICATOR TUBEHAVING A SEGMENTED ELECTRODE AND AN INSULATING SHIELD PLATE Thomas C.Maloney, Bernardsville, and James Thomas Boyer, Plainfield, N.J.,assignors to Burroughs Corporation, Detroit, Mich., a corporation ofMichigan Filed May 20, 1963, Ser. No. 281,434 17 Claims. (Cl. 313-1095)This invention relates to gaseous cold cathode indicator tubes and,particularly, to tubes of the type using groups of cathode segments forproviding character representation.

In segmented tubes of this type, each character is displayed byelectrically connecting and igniting different combinations of cathodesegments. This system of forming characters is well known, and, in fact,several types of electronic display devices have been devised whichutilize combinations of segments to provide displays of differentcharacters. But such devices have not achieved commercial success forone reason or another. For example, some prior art devices are notsutficiently bright, or, if they provide suflicient light output, theymay be relatively complex and expensive. However, all of these devicesare subject to the criticism that the light produced by each of theseveral segments which make up a character does not blend smoothly withthe light produced by other segments, and a smooth, continuous, glowingcharacter is not achieved.

In addition, in order to obtain a character of some size, and to achievesome blending of segment light, known devices generally utilizeindividual segments of unusual shape so that the characters producedhave an abnormal appearance. In addition, because of their unusualshape, all characters do not have the same height and width, and amessage display which includes a large number of characters has anunesthetic and disturbing appearance to the viewer. It has been found,also, that unusually shaped display segments generally do not produceuniform glow over their entire lengths, particularly in cold cathodeglow tubes.

Accordingly, the principles and objects of the present invention concernthe provision of an improved cold cathode segment-type indicator tube.

Briefly, an indicator tube embodying the invention includes a gas-filledenvelope which contains an electrode assembly constructed according tothe invention. The electrode assembly includes a first insulating baseplate which is provided with a plurality of apertures in which glowcathode segments are mounted. The cathode segments are thin, fiat metalstrips, and they are mounted on edge in the insulating base plate. Eachcathode segment includes a pair of ears, which are inserted in anaperture in the base plate and prevent the cathode from moving laterallyin its aperture, and a locking tab, which prevents the cathode frombeing removed from its aperture in the base plate. An insulating shieldplate, having apertures corresponding to and aligned with those in theinsulating base plate, is positioned above and spaced from theinsulating base plate, with its apertures surrounding the associatedcathodes. The shield plate is provided primarily to prevent thedeposition of sputtered cathode metal on the base plate and to preventthe formation of leakage paths between adjacent cathode segments due tosputtered metal. The electrode assembly also includes a metal screenwhich lies between the cathode segments and the tube envelope and servesas an anode and as a trap for sputtered cathode metal.

In the drawings:

FIG. 1 is an elevational view, partly in section, of a tube embodyingthe invention;

3,230,359 Patented Oct. 18, 1966 FIG. 2 is an exploded view of the tubeof FIG. 1;

FIG. 3 is a plan view, partly cut away, of the tube of FIG. 1;

FIG. 4 is a sectional view along the line 44 in FIG. 3;

FIG. 5 is a perspective view, partly in section, of a portion of thetube of FIG. 1; and

FIG. 6 is a perspective view, partly in section, of another portion ofthe tube of FIG. 1.

Referring to the drawings, a gaseous cold cathode indicator glow tube 10includes an envelope 14, of glass or the like, which comprises a base orstem 18 and a bulb 20. The bulb 20 includes a transparent portion 24which serves as a viewing window. The stem 18 carries a plurality ofconductive pins 30, by which the tube electrodes are connected toexternal circuit elements. In the completed tube, the envelope is filledwith a suitable cathode glow supporting gas such as neon, argon, or thelike, and if desired, a quantity of mercury or other heavy, vaporizablesubstance.

The electrode assembly which is mounted inside the tube envelopeincludes (FIG. 2) an insulating base plate 34, of mica or the like,having a top surface 35 and bottom surface 36. The base plate isgenerally rectangular in shape and is provided with a plurality ofapertures 38 which are arrayed in a pattern corresponding to that inwhich the cathode electrode segments 42 are to be arrayed. The apertures38 are narrow, elongated slits which are generally rectangular in shapebut have pointed or otherwise constricted ends 44 and 46. The apertures38 are adapted to receive the cathode electrodes 42, and the constrictedends of the apertures serve to lock the cathodes in position in a mannerto be described below.

The electrode assembly may include any desired number of cathodeelectrodes 42, depending generally on the size of the assembly. In theform of the invention described and illustrated, th rteen Separatecathode electrodes are provided, oriented as shown, and adapted to beconnected in difierent combinations to display numerals zero to nine andseveral letters of the alphabet. The cathodes all lie in a commonstratum.

The cathode segments 42 are thin, flat metal strips which haveconsiderably greater width than thickness. Each segment includes a topedge 48 and a bottom edge 50. The bottom edge of each cathode segmentincludes a raised shoulder portion 56 from which a pair of spacedapartlocking tabs 60 extend. An auxiliary locking tab 64 is provided betweenthe lock-ing tabs 60. A cathode connecting lead 68 extends from one ofthe locking tabs of each cathode. Since each cathode segment is notnecessarily of the same length as every other and since each may haveits own space requirement when mounted in an aperture 38 in base plate34, the location of shoulder 56 and tabs 68 and 64 along the length ofthe cathode may vary for each cathode segment.

The cathodes 42 are mounted on edge on base plate 34, with the shoulders56 bearing against the top surface 35 of the plate and with the lockingtabs 60 and 64 projecting into the appropriate aperturein the insulatingbase plate 34. The locking tabs 60 are wedged into the pointed ends 44and 46 of the aperture, and thus lend rigidity to the cathode mountingand prevent the cathodes from moving laterally with respect to theinsulating plate 34. The auxiliary locking tab 64 is twisted so that itlies perpendicular to the main body of the cathode, bears against thebottom surface 36 of the base plate 34, and locks the cathode inposition on the base plate so that it cannot be pulled or shaken out ofits aperture. The connecting lead 68 of each cathode is welded orsoldered to a tube pin 30, whereby external connection may be made toeach separate cathode segment.

Under some circumstances, which may be determined by the nature of thegas filling of the tube 10, by the cathode materials, and/or by themethod of processing the tube, cathode sputtering may occur, either,generally during tube operation and/ or during the processing of thetube. Under some circumstances, sputtered cathode metal may deposit onthe insulating base plate and may glow, and, under extreme conditions,paths of metal may form on plate 34 between adjacent cathode segments 42to render the tube inoperative. In order to prevent sputtered cathodemetal from adversely afiecting the operation of the tube, an insulatingshield 74, of mica or the like, is provided in the electrode assembly.The shield 74 is in the form of a thin plate, comparable in size andshape to base plate 34, and it is positioned above the top surface ofthe base plate 34. The shield is maintained spaced from the base plateby means of insulating spacer plates 76, of ceramic or the like,positioned between adjacent ends of the shield and base plate. Fasteningmeans such as rivets or eyelets 78 are secured in apertures ,80 in theshield 74, spacers 76, and base plate 34, and

thus hold these three parts together in a unitary assembly.

The shield 74 is also spaced from and is nowhere in contact with any ofthe cathode segments. To this end, the shield is provided with elongatedapertures 84 which correspond in number, shape, and location to theapertures 38 in the base plate 34. However, the apertures 84 in theshield are of such a size that their borders do not touch, but surround(FIGS. 3 and 6), the cathode segments and are larger than the aperturesin the base plate. In addition, the parts are so arrayed that the bottomsurface 50 of the end portions of each cathode are spaced from the topsurface of shield 74. With this arrangement, the base plate 34 isshielded sufiiciently from the cathode segments to prevent anysignificant deposition of sputtered metal on the base plate 34, and thecathode segments are also shielded from each other so that continuousconductive paths of sputtered metal cannot form between adjacent cathodesegments. Such continuous paths would render the tube inoperative.

The electrode assembly of tube 10 also includes a mesh screen electrode90 which acts as a trap for sputtered cathode metal and which is alsoadapted to be used as the tube anode. The screen includes a planarportion 92 which has a size and shape comparable to the size and shapeof plates 34 and 74 and is adapted to overlie all of the cathodeelements and shield them from other portions of the tube, particularlythe viewing window. The portion 92 of screen 90 is spaced from thecathodes and lies between the cathodes and the viewing window. Thescreen 90 also includes two side portions 94 and 96 which depend fromthe long opposite edges of the largearea portion 92, and the lower edgesof the side portions carry one or more locking tabs 100 which engagenotches 104 in the insulating base plate 34 and thereby hold the screen90 in position. The screen also includes a connecting lead 110 which iswelded to a tube pin 30' so that electrical potentials may be applied toit for operation as an anode. The pin 30' carries an insulating sleeve112 to prevent any of the pins 30 from glowing during tube operation.

The entire electrode assembly may be supported by the tube pins, or theassembly may be supported rigidly above the pins by means of the cathodeand anode leads 68 and 110 which are welded to the pins 30.

The completed tube includes a cathode glow supporting gas such as neonor argon, and, in addition, a small quantity of heavy weight substancesuch as mercury to substantially prevent cathode sputtering when thetube is in operation. The mercury may be introduced into tube 10 in anysuitable fashion. For example, a glass tube 120 containing a pellet ofmercury and surrounded by a heating wire 121 may be mounted within thetube envelope, with wire 121 secured to two tube pins 30,

which are provided for that purpose. The tube may be fractured bypassing a heating current through wire 121 at a selected time to freethe mercury and allow it to mix with the gas in the envelope. Themercury might also be provided in an amalgam from which it could bereleased by induction heating.

In operation of tube 10, a positive potential is applied to the anodescreen 90, and a negative potential is applied to selected ones of thecathode segments, depending upon the character to be displayed. Forexample, if it is desired to display the letter I or numeral 1, thencathode segment 42A is energized. If the letter W is to be dis played,then cathode segments 42B are energized. By thus combining selectedcathode segments and applying proper potentials to cause them to glow,various characters may be displayed.

In one manufactured embodiment of tube 10, each cathode segment was madeof stainless steel ribbon having a thickness of about 6 mils, with theheight of each segment above the top surface of disk 34 being about 60mils. In order to obtain smooth blending of glow between adjacentcathode segments, adjacent ends of cathodes were positioned about 10 to15 mils apart.

The present invention has many advantages over the prior art. Oneimportant advantage is that, even though most of the characters whichcan be displayed are made up of a plurality of straight-line segments,each character has an appearance which is quite norm-a1 and quitesimilar to the appearance to which the average viewer is accustomed.Another advantage, which arises from the fact that the cathodes aremounted on edge, lies in the fact that the adjacent ends of adjacentcathodes may be brought sufiiciently close together so that, when twoadjacent cathodes glow, the areas of glow at adjacent ends merge andprovide uniform, continuous glow from one segment to another. Thiscontributes to the normal appearance of a character. In addition, sincethe cathodes are mounted on edge and have their narrow viewing edgesfacing and relatively close to the anode with which cathodes operate, itis likely that cathode breakdown and cathode glow are facilitated.

What is claimed is:

' 1. A gaseous cold cathode glow tube including an envelope having aviewing window,

a gaseous atmosphere within the envelope including an ionizable gas at apressure capable of sustaining cathode glOW,

an anode electrode,

a plurality of flat ribbon-like cathode electrodes mounted in saidenvelope,

said cathodes having considerably greater width than thickness,

an insulating support plate supporting each of said cathode electrodesfrom one edge with the opposite edge facing said viewing window so thatthe glowing edge of a cathode may be viewed,

support means securing each cathode electrode to said support plate,

said cathode electrodes being oriented in a pattern so that selectedones thereof may be connected together to glow as a unit having adesired character representation,

the ends of said cathode electrodes being positioned closely adjacent toeach other so that although each cathode is spaced from the one adjacentto it, when two adjacent cathodes are electrically connected andproperly energized, the glow of one cathode merges with the glow of theadjacent cathode to give the appearance of a single glowing electrode,and

shield means positioned between the glowing edge of each of saidcathodes and said support plate to limit the deposition of sputteredcathode material on said support plate, v

i said shield means comprising a plate spaced from said support plateand including apertures through which said support members pass withouttouching said shield means. 2. The tube defined in claim 1 and includinga fine mesh screen positioned between said cathodes and said viewingwindow as a trap for sputtered cathode material.

3. A gaseous cold cathode glow tube including an envelope having aviewing window,

a plurality of cathode electrodes lying in a common stratum within saidenvelope for viewing through said viewing window,

said cathodes comprising metallic strips having considerably greaterwidth than thickness;

an insulating base plate supporting each of said cathode electrodes fromone edge with the opposite edge of each cathode facing said viewingwindow so that the glowing edge of a cathode is viewed when a cathodeglows,

each cathode and said base plate having cooperating means for lockingeach cathode in position on said base plate,

a shield plate including means spaced from each cathode electrode andshielding said base plate from said cathodes whereby sputtered cathodematerial is substantially prevented from depositing on said base plate,

and a mesh screen anode overlying and enclosing said cathode electrodeand lying in operative relation with each cathode.

4. A gaseous cold cathode glow tube including an envelope having aviewing window,

a plurality of cathode electrode segments lying in the same stratum,

each said cathode segment comprising a metallic strip havingconsiderably greater width than thickness and having attached supportmeans,

an insulating base plate for supporting each of said cathode electrodesfrom one edge with the opposite edge of each cathode facing said viewingwindow so that the glowing edge of a cathode is viewed when a cathodeglows,

said base plate having a plurality of apertures for receiving thesupport means attached to said cathode segments,

each support means comprising a plurality of tabs on one edge of acathode segment for insertion into said apertures in said base plate,

a shield plate including means spaced from each cathode segment and itssupport-means and shielding said base plate from said cathodes wherebysputtered cathode material is substantially prevented from depositing onsaid base plate,

and a mesh screen anode overlying and enclosing said cathode segmentsand lying in operative relation with each cathode.

5. A gaseous cold cathode glow tube including an envelope having aviewing window,

a plurality of cathode electrode segments lying in the same stratum,

each said cathode segment comprising a metallic strip havingconsiderably greater width than thickness and having attached supportmeans,

an insulating base plate for supporting each of said cathode electrodesfrom one edge with the opposite edge of each cathode facing said viewingwindow so that the glowing edge of a cathode is viewed when a cathodeglows,

said base plate having a plurality of apertures for receiving thesupport means attached to said cathode segments,

each support means comprising a pair of tabs on one edge of a cathodesegment for insertion into said apertures in said base plate to preventlateral movement of the cathode and a locking tab which engages saidbase plate and prevents the cathode from being removed from its aperturein the base plate,

a shield plate including means spaced from each cathode segment and itssupport means and shielding said base plate from said cathodes wherebysputtered cathode material is substantially prevented from depositing onsaid base plate,

and a mesh screen anode overlying and enclosing said cathode segmentsand lying in operative relation with each cathode.

6. The tube defined in claim 5 wherein the apertures in the base plateare generally rectangular in form and have their ends constricted, thepair of tabs of each cathode 'being spaced apart and engaging theconstricted ends of an aperture and the locking tab being positioned toengage the base plate to prevent the cathode from being pulled out ofthe aperture.

7. The tube defined in claim 5 wherein the apertures in the base plateare generally rectangular in form and have their ends constricted, thepair of tabs of each cathode being spaced apart and engaging theconstricted ends of an aperture and the locking tab being positionedbetween said tabs and being twisted transversely to the long axis of theaperture to engage the 'base plate to prevent the cathode from beingpulled out of the aperture.

8. The tube defined in claim 5 wherein said anode includes a firstlarge-area portion which lies between said cathodes and said viewingwindow and parallel to said cathodes, said anode also including sideportions 'which extend downwardly from said large-area portion andengage said base plate whereby said anode is held in place.

9. The tube defined in claim 5 wherein said anode includes a firstlarge-area portion which lies between said cathodes and said viewingwindow and parallel to said cathodes, said anode also including sideportions which extend downwardly from said large-area portion, said sideportions having locking tabs which engage said base plate whereby saidanode is held in place.

10. The tube defined in claim 5 wherein insulating spacers are providedbetween said base plate and said shield plate and a fastener is providedto secure said plate, said spacer, and said shield in a unitaryassembly.

11. The tube defined in claim 5 wherein insulating spacers are providedbetween said base plate and said shield adjacent opposite ends thereofand a fastener is provided threaded therethrough to secure said plate,said spacer, and said shield locked together in a unitary assembly.

12. A gaseous cold cathode glow tube including an envelope having aviewing window,

an ionizable gas in said envelope for sustaining cathode glow,

a plurality of cathode electrodes lying in a common stratum within saidenvelope for viewing through said viewing window,

said cathode electrodes comprising elongated metallic members.

an anode electrode in operative relation with said cathode eectrodes,

an insuating base pate supporting each of said cathode electrodes facingsaid viewing window so that the glowing length of a cathode is viewedwhen a cathode glows,

each cathode and said base plate having cooperating means for lockingeach cathode in position on said base plate, and

a shield plate of insulating material positioned between said cathodesand said base plate and shielding said base plate from said cathodeswhereby sputtered cathode material is substantially prevented fromdepositing on said base plate,

said shield plate having apertures through which said cooperating meansextends between said cathodes and said base plate without coming incontact with said shield plate.

13. A gaseous cold cathode glow tube including an envelope having aviewing window,

a gaseous atmosphere within the envelope including an ionizable gas at apressure capable of sustaining cathode glow,

a plurality of elongated cathode electrodes mounted in said envelope tohave a lengthwise viewing surface facing said viewing window, theviewing surfaces of said cathodes lying in a common plane,

an anode electrode in the envelope positioned in operative relation withsaid cathode electrodes,

21 base member of insulating material having a continuous surface,

a plurality of support members supporting the cathodes from the basemember, each of the cathodes being supported at least at one point byone ofsaid support members,

a plurality of conductive leads each connected to one of the cathodesfor selectively energizing the cathodes and producing a cathode glow atleast along the viewing surface thereof, and

a shield member of insulating material disposed generally parallel tothe base member and lying between the viewing surfaces of the cathodesand the base member, the shield member having a plurality ofspaced-apart apertures, each of which is aligned with one of the supportmembers, the sizes of the apertures being larger than the cross-sectionof the respective support members and being in registry with the supportmembers such that the support members pass through the apertures withouttouching the edges thereof, whereby the shield member is at all pointsspaced from the support members and does not form a continuous surfacebetween any two such members, the spaces between the shield member andthe support members containing only the gaseous atmosphere,

the shield member also being spaced from the base member and thecathodes, and serving to intercept sputtered material from the glowingportions of the cathodes to prevent the formation of a continuousconductive path of sputtered material along the surface of the basemember and electrical short circuits between two or more of the supportmembers.

14. A cold cathode glow .tube in accordance with claim 13 wherein thesupport members are made of conductive material and their conductivesurfaces are exposed.

15. A cold cathode glow tube in accordance with claim 13 wherein thesupport members lie closely adjacent to the edges of the apertures insaid shield member.

16. A cold cathode glow indicator lamp in accordance with claim 13wherein the cathodes are arranged in the pattern of a character andselective groups are energiza-ble to display different glow characters,and have contiguous portions so that the glow characters areuninterrupted.

17. A cold cathode glow indicator lamp in accordance with claim 13characterized by at least one spacer interposed between the shieldmembcr and the base member.

References Cited by the Examiner UNITED STATES PATENTS 2,632,128 3/1953Hancock 313-210 X 2,783,408 2/1957 Williams et al 3l3209.5 2,833,9495/1958 Driscoll 313109.5 3,041,491 6/1962 Cistola 3l3109.5 X

R. JUDD, Assistant Examiner. GEORGE N. wEsTBY, Examiner.

JAMES W. LAWRENCE, Primary Examiner.

1. A GASEOUS COLD CATHODE GLOW TUBE INCLUDING AN ENVELOPE HAVING AVIEWING WINDOW, A GASEOUS ATMOSPHERE WITHIN THE ENVELOPE INCLUDING ANIONIZABLE GAS AT A PRESSURE CAPABLE OF SUSTAINING CATHODE GLOW, AN ANODEELECTRODE, A PLURALITY OF FLAT RIBBON-LIKE CATHODE ELECTRODES MOUNTED INSAID ENVELOPE, SAID CATHODES HAVING CONSIDERABLY GREATER WIDTH THANTHICKNESS, AN INSULATING SUPPORT PLATE SUPPORTING EACH OF SAID CATHODEELECTRODES FROM ONE EDGE WITH THE OPPOSITE EDGE FACING SAID VIEWINGWINDOW SO THAT THE GLOWING EDGE OF A CATHODE MEY BE VIEWED, SUPPORTMEANS SECURING EACH CATHODE ELECTRODE TO SAID SUPPORT PLATE, SAIDCATHODE ELECTRODES BEING ORIENTED IN A PATTERN SO THAT SELECTED ONESTHEREOF MAY BE CONNECTED TOGETHER TO GLOW AS A UNIT HAVING A DESIREDCHARACTER REPRESENTATION, THE ENDS OF SAID CATHODE ELECTRODES BEINGPOSITIONED CLOSELY ADJACENT TO EACH OTHER SO THAT ALTHOUGH EACH CATHODEIS SPACED FROM THE ONE ADJACENT TO IT, WHEN TWO ADJACENT CATHODES AREELECTRICALLY CONNECTED AND PROPERLY ENERGIZED, THE GLOW OF ONE CATHODEMERGES WITH THE GLOW OF THE ADJACENT CATHODE TO GIVE THE APPEARANCE OF ASINGLE GLOWING ELECTRODE, AND SHIELD MEANS POSITIONED BETWEEN THEGLOWING EDGE OF EACH OF SAID CATHODES AND SAID SUPPORT PLATE TO LIMITTHE DEPOSITION OF SPUTTERED CATHODE MATERIAL ON SAID SUPPORT PLATE, SAIDSHIELD MEANS COMPRISING A PLATE SPACED FROM SAID SUPPORT PLATE ANDINCLUDING APERTURES THROUGH WHICH SAID SUPPORT MEMBERS PASS WITHOUTTOUCHING SAID SHIELD MEANS.